The communication mode of the universal serial bus (USB) adopts a client-server type which operates in the form of tiered star topology architecture. Generally speaking, only one USB host can be used in the tiered star topology architecture. The USB host in the tiered star topology architecture is a control center. The USB hub generates a plurality of tiered nodes and each node is connected to downstream USB hubs or USB devices. The USB host connected to the USB hub controls the USB hub for accessing the USB devices via the USB hubs. The USB devices may be a keyboard, a mouse or storage drives utilized in a computer system. Generally, USB bus adopting the client/server type and operated in the tiered star topology architecture only allows the USB host to communicate with the USB device at a peer-to-peer mode and access the data stored in the USB device. In other words, if it is necessary that one USB device communicates with another USB device under the control of the USB host, the USB host needs to dominate the operation of the communication with the USB devices. While a plurality of USB devices desire to communicate with the USB host, each USB device utilizes the time-sharing scheme for exchanging data with the USB host.
When one USB device needs to disadvantageously communicate with another USB device, the two USB devices first communicate with the USB host, respectively and the USB host then transfers the data from one USB device to another USB device. As shown in FIGS. 1A-1B, they illustrate conventional schematic diagrams of USB device which is selectively controlled by USB host and USB OTG (on-the-go) device. The USB OTG device manually serves as either a USB device or a USB host. That is, the USB OTG device cannot implement the functions of USB device and host synchronously. In FIG. 1A, the USB OTG device 100 in a digital photo frame 106 is selectively switched to be connected to the USB host 102 when the USB OTG device 100 serves as a USB device and the USB host 102 desires to access the USB OTG device 100. In FIG. 1B, the USB OTG device 100 is selectively switched to be connected to the external USB device 104 when the USB OTG device 100 serves as a host and the USB OTG device 100 desires to access the external USB device 104. It is quite inconvenient for the system since the USB OTG device 100 is incapable of directly communicating with the external USB device 104 and USB host 102.
Consequentially, there is a need to develop a novel electronic apparatus among the USB devices and the USB host to solve the above-mentioned problem.